China’s Z.ai says new model nears Anthropic’s Mythos 5 in cyber-defence tests

CHALLENGING CLOSED-SOURCE MYTHOS

Z.ai framed the launch as a challenge to the restricted-access model represented by Mythos. It argued that advanced cyber-defence tools should be available to developers of open-source software and smaller security teams, rather than being controlled by a limited number of closed-model providers.

It said it would begin an “Open Source Shield” initiative to audit selected open-source projects, provide model access for defensive work and add code-auditing functions to its ZCode programming product.

“In this spirit, Z.ai appears to be proposing a kind of ‘Project Glasswing’ with Chinese characteristics that sees openness as an asset rather than a drawback,” said Wagner, referring to the consortium of Western companies with access to Mythos.

New York-based AI startup Hugging Face last month said it used Z.ai’s previous model GLM-5.2 to defend against a cyberattack by a rogue OpenAI agent that broke into its systems.

Z.ai is not the first Chinese company to position a product as an answer to Mythos. Cybersecurity firm 360 said in June that its Tulongfeng vulnerability-discovery system had achieved Mythos-equivalent capabilities by combining AI models with security data and automated tools, though those claims were not independently verified.

GLM-5.3 differs in that it is a general-purpose coding model that Z.ai says acquired cybersecurity capabilities through expanded post-training and reinforcement learning, rather than a purpose-built security system. 

The company said it used the same base model as GLM-5.2 but trained it in longer and more varied task environments.

The launch builds on global interest in GLM-5.2, which gained attention in recent months among overseas developers for coding and agent capabilities that users and analysts said approached leading US models but at a much lower cost.